[Regeneration, differentiation and moulting hormones in the cockroach embryo cultured in vitro]. / Régénération, différenciation et hormones de mues chez l'embryon de blatte en culture in vitro.

1. The second moulting cycle of the cockroach embryo may be divided into 2 parts: during the first one, regeneration of appendages is possible in embryos cultured in vitro; it is not possible during the second part. 2. Regeneration takes place inside the cuticle of the stump in 4 phases: 1) epidermal wound healing; 2) morphallaxis; 3) growth by cell proliferation; 4) secretion of the cuticle. 3. The regenerative capacity does not seem to depend on hormonal secretions and is apparently an intrinsic property of the epidermal cells of the appendages. 4. The addition of exogenous moulting hormone to the culture medium inhibits the regeneration and causes precocious formation of spines and hairs and secretion of the cuticle. 5. A relatively short period of contact (24 to 30 h) with the hormone triggers a chain of processes which then continue in its absence (formation of spines and hairs, secretion of the epicuticle and then of the procuticle). 6. There is an incompatibility between regeneration and differentiation, as if these two functions corresponded to two progammes, one of which is inhibited and the other triggered by a high concentration of hormone. 7. The moulting hormone is not produced exclusively by the prothoracic glands.

Ecdysteroid titres during ovarian and embryonic development inBlaberus craniifer.

InBlaberus craniifer, the maturation of the oocytes is accompanied by morphological modifications of the surrounding follicular cells and by variations in the ecdysteroid titre.Before the follicular cells form the chorion, they synthesise ecdysteroids which pass into the terminal oocytes to be stored. During the secretion of the chorion, before the release of the oocytes, one observes a decrease of the ecdysteroid titre in the ovaries. The hormonal titres in ovaries and haemolymph fluctuate in parallel, probably because ovaries "leak" into the haemolymph.The terminal oocyte of each ovariole is deposited into the incubating pouch where the entire embryonic development takes place. There is first a decrease of the ecdysteroids synthesised by the follicular cells and stored in the eggs. One then observes 3 ecdysteroid peaks during each of the 2 cycles of the development. During the first cycle, the first peak coincides with the end of the metamerisation, the second peak with the secretion of the first cuticle and the third with the transition between the first and the second cycle. For the second cycle, the first peak coincides with the loss of the capacity to regenerate, the second with the secretion of the second cuticle and the third with the hatching period.The third peak of each of these 2 cycles is atypical compared with what is known of the larval cycles. The analysis of the hatching peak has shown that it is principally composed of a compound more polar than α-ecdysone.

Positional cell surface antigens in an insect appendage.

Mice were immunized with membrane preparations of epidermal cells taken from different parts (internal and external face of femur and apex and base of tibia) of the metathoracic legs of cockroach larvae. Using indirect immunofluorescence, anti-internal face of femur antibodies were observed to bind preferentially to membranes from the internal face of the femur; similarly, anti-external face of femur antibodies bound preferentially to membranes from the external face of the femur. We also found a preferential binding of anti-apex of tibia antibodies to membranes from the apex of the tibia and anti-base of the tibia antibodies to membranes from the base of the tibia. When anti-tibia sera were tested on membranes from the femur, anti-apex of tibia antibodies bound preferentially to membranes from the apex of the femur, and anti-base of tibia antibodies bound preferentially to membranes from the base of the femur.This demonstrates that epidermal cell membranes from the different parts of the leg differ in their antigenic properties, and that these differences are related to their position around the appendage and along the proximodistal axis of segments.These results are in agreement with those of previous graft experiments and with the concept of ordered sequences in insect appendages.